Actually I was on another forum and was asked to ask this question on this forum. I am just learning about Air Conditioners, and have a few questions, anyhow here it is in a nut shell. On a reversing valve selonoid, window unit AC heatpump, if there is voltage, 120 at the reversing valve, does that normally mean that the selonoid is bad if the unit is blowing cold air in heating mode. Or can the switch, reversing valve or thermostat be stuck. Thanks. Enquiring minds want to know.

Let's state the correct operation of a "Four Way Valve" commonly called a reversing valve.On a call for heat, the solenoid is energized causing the valve to allow the change of direction of refrigerant flow from the compressor to the indoor coil which will bow reject heat into the conditioned space. On a call for cooling, the solenoid valve is de-energized allowing the flow of refrigerant from the compressor to flow to the outdoor coil rejecting heat to the surrounding or ambient air.If you need further explanation please read "Heat Pumps" by "Professor Eugene Silberstein" from Delmar division of Cengage publishing of which I am a "Technical Reviewer" for.

That is a beautiful looking reversing valve, simply beautimus. I know how a reversing valve works. But, I am stuck in a delema. This pertains to window heat pump ac units. I have a question. If a reversing valve has 0 volts across it. And the defrost control has 120 volts across it, and the unit is blowing cold air with the thermostat in heating mode, and from what I understand from earlier posts, when measuring voltage across a switch, and I presume the defrost control is a switch, then wouldn't the defrost control be the culprit here, since a voltmeter across a switch will measure 120 when the switch is open and 0 volts when the switch is closed, wouldn't the defrost control do the same. Info. appreciated, when you say Green, you don't mean I am a tree hugger do you! ;

Patience "Grasshopper" will win out all the time, and Reading Is Fundamental. Why not buy the Heat Pump book (no I do not make money) and learn all the right information.You will be rewarded two ways. 1. Educated rather than Guesstimated 2. Profitable, you can enter this business with a solid background.I say Green as someone inexperienced, but looking to learn.

That is a beautiful looking reversing valve, simply beautimus. I know how a reversing valve works

If you don't need know how the valves work, just say so. The way you presented the post is far different from what you say now.

From your first post

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On a reversing valve selonoid, window unit AC heatpump, if there is voltage, 120 at the reversing valve, does that normally mean that the selonoid is bad if the unit is blowing cold air in heating mode. Or can the switch, reversing valve or thermostat be stuck.

I think I covered it. Solenoids have continuity if they are good. You're still stuck in electricity 101

I don't mind reading a book, that is what I am doing now I checked out some of the stuff in the links you provided. Where is the book. I am concerned with 120 volts not 240. I am asking a question pertaining to ac window units. The stuff I checked out in your link pertains to 240. Now I know 240 has 2 hot wires and one ground. As 120 has a neutral a hot and a ground. Now in 120 from what others have told me on this site, a switch on the same line whan volts are measured across it will give one of two readings, either 120 if the switch is open, 0 if it is closed. Other techs on this site have told me this. I checker out a couple links you provided on HVAC voltage measurements and that information tells me on a 240 line, same line, if a volt meter is across the switch, no matter what, if the switch is open or closed the meter will measure o volts unless the meter on one side goes to ground. So, there is something missing here, what is the difference, between 240 on the same line with a switch or 120 with a switch. Of course I know that 240 is 120 times 2, and one line is 120 and so is the other with one ground, now 120 is two hots with one hot and one neutral and a ground. Can you please explain this to me, all I need is a simple explanation of the truth, and the truth will set me free. If you know of a link that explains voltage measurements and 120 service please let me know, so I can get on with my life, ThankYou!